All excellent points... I guess I should have said "ideally"....I'm finding more and more that manufacturers are indeed catering to certain facets...I'm not yet decided if that's a good or bad thing. The 600/650s come from the old school philosophy in being a palatable compromise, bridging many genres and probably the reason they've endured their popularity, the 650s veered slightly IMHO in the early 90's once the emerging home theater and the use subs came into use. But by today's standards and music their base extension is rather wanting for many.... as may be their overall presentation and dynamics especially with the prevailing onslaught of over compressed music and the loudness wars. From what I've gathered so far the 660s does appear to be sitting on the fence, which makes sense in many ways if it is indeed to be a "modern" successor to the venerable 600 series. So...you could be quite correct...it's a challenge for any manufacture to currently appease all tastes as folks are looking for a devise to "enhance" their chosen genres, so it's not to say that one headphone cannot be manufactured/ used for all types of music as I believe we can agree that they are only reproducing recorded sound waves...but personal preferences and listening habits dictate otherwise.